E1-M3A

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Project title and acronym

Ageing of Composites in Deep-water Environment (AGE-CO-DEEP)

Host facility

POSEIDON E1-M3A (Hellenic Centre for Marine Research)

Modality of Access

MoA2 – Partially remote (the presence of the user is required at some stage, e.g. for installing and uninstalling an instrument)

Description

Composites materials are used in the marine, offshore and underwater industry for decades, due to their intrinsic properties, e.g. lightweight structures compared to metallic ones of equal strength, corrosion resistant, etc. More specifically, the demand for composite materials in deep-water applications and in primary applications within the Offshore Oil & Gas industry and deep-water vehicles (e.g. Automated Underwater Vehicles) has been increasing rapidly the last 10 years. This trend is expected to continue in the aforementioned sectors, but also in other sectors such as

Oceanography for deep-water exploration, as further integration of composite materials in underwater structures is rigorously pursued. With respect to the composite materials used, the constituents are, mainly, glass or carbon fibres mixed with a matrix material (polymeric resin). Glass fibre composite material is the most widely used, due to the combination of low cost to adequate strength, but carbon fibre composites are gaining market share in the deep-water applications, especially due to their excellent high strength and low weight combination. These features along with other specific advantages (facilitation of easier underwater deployment, buoyancy, thermal isolation, non-corrosive, etc.) strongly favour the use of composites. Nevertheless composite materials can be affected by degradation mechanisms, like:

• Structural damage due to static loading under hydrostatic pressure, sometimes combined with creep, dynamic and impact loads

• Ageing due to absorption

• Biological attack.

More particularly, in a scenario of prolonged underwater use of composite material structures, the physical and mechanical properties can be degraded by the attacks on the matrix material (resin) and/or the fibres, which can be manifested in the degradation of the interface between matrix and fibre, reinforcement, the interface between two adjoining plies (delimination), etc. The phenomenon is called ageing of composites and is very critical for composite underwater structures that operate for prolonged periods of time. Studying ageing effects of composites may address many of the uncertainties, related with the long-term performance of composites under conditions encountered in service.

In   this   context,   the   long-term   behaviour   of   composite   materials   in   the   deep-water environment will be studied. Environmental parameters of the deep-sea that affect durability will  be measured  in  situ,  and  the  structural  behaviour  of  composite  specimens  will  be monitored for a period of 18 months. Moreover the aged specimens will be recovered after the end of 18 months and tested in laboratory environment and quantify the effect of ageing on mechanical properties of the studied composite materials.

The  POSEIDON  infrastructure  of  the  Hellenic  Center  for  Marine  Research  provides  the necessary environmental information and the appropriate operational and technical facilities for  an  18  months  ageing  study  of  a  series  of  composite  specimens  in  the  depth  of approximately 1.000 meters. The POSEIDON M3A station monitors at several depths environmental parameters like sea temperature, salinity, dissolved oxygen, currents, biogeochemical parameters and sediment composition including deposition rate.

The advantage that is offered by conducting these experiments linked with the POSEIDON infrastructure is, that the degradation mechanisms and the recorded data from the specimens can be linked to the environmental parameters that the POSEIDON station monitors and useful correlations can be deducted which can aid in the identification and quantification of the ageing mechanisms which promote the degradation of the mechanical properties of the tested composites specimens.

The long-term environmental and load effects to the composites will be examined and measured. The results will be used from ALS in order to excide its material knowledge and experience beyond the existing state of the art. The ageing of the composites is an open and unexplored research field especially for the deep-water environment.